Butinediol using catalyst prepared from synthetic malachite

ABSTRACT

Synthetic malachite of desirable particle size and distribution is coprecipitated with small amounts of uniformly dispersed bismuth. After nucleation, the crystals are grown at elevated temperatures. The malachite can be converted into a cuprous acetylide complex useful as an ethynylation catalyst.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 794,674, filedMay 6, 1977 now U.S. Pat. No. 4,107,082; which in turn is a continuationof application Ser. No. 687,179, filed May 17, 1976; now abandoned,which is a continuation-in-part of application Ser. No. 445,476, filedFeb. 25, 1974, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a process for coprecipitating malachite withbismuth, to a process of making a cuprous acetylide complex ethynylationcatalyst starting with such coprecipitation, and to the complexproduced.

In the production of 1,4-butynediol by the reaction of acetylene withformaldehyde in the presence of a cuprous acetylide complex catalyst, itis known to be desirable to inhibit the formation of cuprene,polymerized acetylene, by the use of inhibitors such as bismuth oxide.U.S. Pat. No. 2,300,969--Reppe et al. (1942) discusses the use ofseveral such inhibitors in the formation and use of such catalysts atelevated pressures such as about 20 atmospheres. U.S. Pat. No.3,650,985--Kirchner (1972) mentions the utility of bismuth oxide as acuprene inhibitor in cupric acetylide catalyst made and used at lowpartial pressures of acetylene, below 2 atmospheres. Neither of thesepatents indicates how the bismuth values can be incorporated uniformlyinto the catalyst itself.

It has been found that in the production of the low pressure catalystsaccording to U.S. Pat. No. 3,650,985, if bismuth oxycarbonate is addedseparately to preformed malachite, it will separate in the catalystwhich is eventually prepared, leading to unsatisfactory results. Thus,it is desirable to have a satisfactory method of coprecipitating bismuthin the basic cupric carbonate or malachite which is the catalystprecursor.

Basic copper carbonate, known as malachite, Cu₂ (OH)₂ CO₃, is normallyprepared by either of two precipitation techniques. In the first, asolution of a copper salt such as copper nitrate or chloride isneutralized to a pH of 7.0 with sodium or potassium carbonate orbicarbonate. Initially, hydrated copper carbonate, amorphous CuCO₃.x(H₂O), precipitates in the form of a thick gelatinous material which, onheating, slowly converts to malachite with the elimination of CO₂.Precipitates of crystals of malachite made by this technique generallycomprise irregularly shaped particles ranging in size from less than 1micron (μ) to more than 25μ in average particle cross-sectionaldimension. If the gel has set up thoroughly, then the irregularity andbroad distribution of crystallite size on crystallization seem to be aresult of tearing of the gel as it precipitates. The irregularly-shapedcrystallites and wide distribution of particle size is ratherundesirable for use as a precursor in the production of cuprousacetylide ethynylation catalysts.

Another method for the precipitation of malachite involves feedingsimultaneously the copper solution and the carbonate neutralizationagent with agitation to maintain a pH in the range of 5 to 8. Thehydrated copper carbonate so obtained is also subsequently converted tomalachite at ambient temperature or more rapidly as the temperature isincreased. This technique produces a more regular crystalline productwhich consists of agglomerates of individual crystallites of about 2 to3μ average cross-sectional dimension. The agglomerates range in size upto a maximum of about 30μ. As with the first method of adding thecarbonate neutralizer to the copper solution, so too with this method ofsimultaneously feeding them together, an amorphous hydrated coppercarbonate is initially formed.

It would be desirable to have a process for the production of basiccopper carbonate crystalline particles having bismuth incorporatedtherein with the particles being of a fairly uniform and relativelylarge particle size. The uniformity of dispersion of bismuth in theparticles is desirable to permit the formation of ethynylation catalystin which the bismuth values will remain in place and continue to beeffective in the prevention of cuprene formation.

SUMMARY OF THE INVENTION

The present invention provides a process for the production ofcrystalline particles of basic copper carbonate having uniformlydispersed therein bismuth in amounts in the range of 2 to 5 percent byweight based on the amount of copper present. The process comprisesthree steps. First, hydrated copper carbonate particles are precipiatedby the addition to water, preferably simultaneously, of solutions ofcupric salts and alkali metal carbonate or bicarbonate to form areaction mixture. The solutions are in such proportions as to maintainthe pH about in the range of 5.0 to 8.0. Then the hydrated coppercarbonate is converted to basic copper carbonate in the reaction mixtureat a temperature of at least about 60° C. This conversion occurs throughthe nucleation of crystallites of malachite from the amorphous hydratedcopper carbonate. Subsequent additions of copper, bismuth and carbonateprecipitate on these converted nuclei as more malachite. The nucleatedcrystalline particles and agglomerates of such particles are grown whilethe bismuth is incorporated uniformly into the particles. The reactionmixture is kept at temperatures of at least about 60° C. during thegrowth. The solutions of cupric salts, bismuth salts and sodiumcarbonate or bicarbonate are added in such proportions as to maintainthe pH about in the range of 5.0 to 8.0 until the averagecross-sectional dimension of the agglomerates of crystallites is atleast about 10 microns.

The bismuth content herein is expressed in terms of percent by weightbased on the amount of copper present. Parts, percentages andproportions herein are by weight except where indicated otherwise.

Although it is necessary to have the bismuth present during the particlegrowth, it is also desirable and, as a practical matter may benecessary, to have it present also during the precipitation andnucleation steps.

The coprecipitated basic copper carbonate-bismuth particles can be usedto make a cuprous acetylide complex useful as an ethynylation catalyst.The basic copper carbonate-bismuth particles are subjected as a slurryin aqueous medium at 50° to 120° C., to the simultaneous action offormaldehyde and acetylene at a partial pressure of not more than 2atmospheres. The aqueous medium has a pH of 3 to 10 at the initiation ofthe subjecting. Preferably, the reaction is continued until all of thecupric precursor is converted to the cuprous acetylide complex. It isdesirable for the medium in which the subjecting is done to have a pH inthe range of 5 to 8 at least initially.

The resulting catalysts made from such precursors are a particulatecuprous acetylide complex which consists essentially of copper, carbon,hydrogen, oxygen and bismuth in proportions corresponding to the generalformula

    (CuC.sub.2).sub.2 (CH.sub.2 O).sub.x (C.sub.2 H.sub.2).sub.y (H.sub.2 O).sub.z --Bi

wherein, when w = 4, x = 0.24 to 4.0, y = 0.24 to 2.40 and z = 0.67 to2.80, and in which the bismuth is present in an amount of 2 to 5%. Thecomplex particles have a total surface area of at least 5 m.² /g., andthe average particle cross-sectional dimension is at least 10μ.

Preferably, the particulate complex has a total surface area of 15 to 75m.² /g., the average particle cross-sectional dimension being in therange of 10 to 40μ, containing 20 to 66% copper, 2 to 12.5 carbon atomsper copper atom, 0.2 to 2 hydrogen atoms per carbon atom, 0.1 to 1oxygen atom per carbon atom, and 3 to 4% bismuth.

DETAILED DESCRIPTION

In contrast to the basic copper carbonate crystal production methods ofthe prior art, the method of the present invention utilizes a rapidprecipitation of hydrated copper carbonate followed by nucleation andconversion of the hydrated copper carbonate to basic copper carbonate(malachite). The nucleation and conversion are encouraged by an elevatedtemperature, such as over 60° C. The larger proportion of the reactantsfor forming the basic copper carbonate, such as at least two-thirds ofthe copper, is not added to the reaction mixture until after theconversion to basic copper carbonate. At this time, the copper salts,neutralizing chemicals and bismuth combine readily to produce a uniformdispersion of bismuth in basic copper carbonate crystalline particles ofrather uniform and large particle size. This crystal growth avoids theinitial formation of further gelatinous hydrated copper carbonate.

If the entire production of the basic copper carbonate crystals is doneat elevated temperatures such as over 60° C., including precipitation,nucleation and growth, the hydrated copper cabonate is not present formuch time at all. Nucleation and conversion occur rapidly, and growth ofthe initial nuclei is the main phenomenon occurring. Thus, operating allsteps of the production at elevated temperature leads to the productionof smaller numbers of larger particles. Actually, each of the steps willtake place at lower temperatures such as room temperature, about 23° C.Many nuclei would form and convert to malachite before crystal growthdepleted the concentration of reactants, leading to the prevalence ofsmaller particle sizes. Also, with malachite production at lowertemperatures, the bismuth values are not uniformly included in the basiccopper carbonate made this way but tend to segregate either duringformation of the carbonate or later during use of the carbonate to formcuprous acetylide complexes for use as ethynylation catalysts. Thus, itis important to use the procedure of the invention to form the basiccopper carbonate-bismuth coprecipitates to be used in making theethynylation catalysts.

For the production of smaller-sized crystallites and agglomerates, thenucleation can be conducted at a lower temperature followed by anincrease in temperature to above 60° C. for relatively rapid conversionand growth and uniform dispersion of the bismuth. For the production oflarger-sized crystallites and agglomerates, the nucleation also would beconducted at a higher temperature such as above 60° C.

If the pH is raised at least 1.0 unit between the nucleation step andthe growth step, this can lead to even greater uniformity in particlesize. Crystal growth occurs optimally in a band representingsuper-saturation on a plot of solubility versus temperature. Thesuper-saturation band is wider for these products at higher pH values.Therefore, higher pH within limits will lead to more deposition onexisting nuclei and less formation of new small nuclei if the reactioncontinues to be conducted in the super-saturation band.

The conversion of the hydrated copper carbonate to malachite as themalachite nucleates can be readily observed. Hydrated copper carbonateis blue and it tends to be a structureless gelatinous mixture. Themalachite is green and crystalline.

If sodium carbonate is added to a copper nitrate solution having a pH of3, as the pH rises to 41/2 the reaction product sets up as a thick gel.Further pH rise and agitation break up the gel, tearing as it convertsto malachite to form very irregular particles related to the size of thetorn gel. Above a pH of about 8.0, and at elevated temperatures theamorphous copper carbonate hydrate begins to convert to copper oxidewhich is undesirable. Below a pH of 5.0, the gel formation becomestroublesome.

During the catalyst production, sodium iodide can be added separately.This produces some bismuth oxyiodide in the catalyst which acts as afurther inhibitor for cuprene formation.

The catalyst is desirably about 15 to 20μ agglomerate size. Largerparticles have advantages over smaller particles including more rapidfiltration and drying, lack of dust formation and lack of band formationon settling. Fifty μ agglomerate size is larger than desirable due todecreased activity of the catalyst. Catalyst particles that are toosmall lead to filtering difficulties. The size of the agglomerates canbe readily controlled by adjusting the temperature and pH of the stepsof the production of the basic copper carbonate.

During the ethynylation reaction, acetylene inhibits the valence changeof cuprous copper in the catalyst to elemental copper or cupric copper.This is desirable, because elemental copper is a catalyst for thepolymerization of acetylene to cuprene. Cuprene is quite undesirable inthese reactions because it tends to clog filters and cannot be readilyremoved. During some upset conditions in production operations, the flowof acetylene into the reactor is shut off due to emergency or suddenloss of supply. Bismuth, such as in the form of oxycarbonate uniformlyincorporated in the catalyst, aids in protecting the catalyst from suchdegradation even while hot and in the absence of acetylene.

Above 4 or 5% bismuth, a second phase tends to separate from thecatalyst after some weeks of operation in the ethynylation catalyst.This manifests itself in the formation of fine particles which causefilter difficulties. Also, such separation would tend to degrade theoperation of the bismuth in the catalyst.

With a solubility level in the ethynylation reaction media of about 0.5ppm, bismuth can be digested out of the catalyst. This is more of aproblem if the bismuth content of the catalyst is over about 3%, but itis not a serious problem until above about 5% bismuth content.

In preferred techniques according to the invention, bismuth nitrate inthe desired concentration is dissolved in the copper nitrate solutionwhich is then fed with sodium carbonate to a crystalizer, preferablysimultaneously. In batch operations one could be fed into the other, andfor semicontinuous operation an excess of one could be fed to a heelcontaining the other. The pH is maintained between 6 and 7, and thetemperature is in the 60°-80° C. range during crystal growth. For largercrystals, the temperature is also in that region initially for theprecipitation and nucleation. In the resulting malachite, the bismuth iseffectively coprecipitated and uniformly dispersed. When suchbismuth-containing malachite is utilized to form a cuprous acetylidecomplex ethynylation catalyst for butynediol synthesis, a substantialimprovement in catalyst filterability and stability results.

Bismuth-containing malachite has been prepared according to theinvention using early nucleation techniques but with bismuthconcentrations of 1, 2, 3, 4, 8, 10 and 15%. The resulting malachite wasthen used to prepare the ethynylation catalysts. Catalysts thus obtainedwere then subjected to extended life tests to determine the improvedstability and operability as indicated by the absence of cupreneformation. For comparative purposes, catalysts were also made with acommercial grade of malachite. Life tests were run for a period of about100 hours or more at which time the catalyst was removed and examinedfor the presence of cuprene. Cuprene is readily detected visibly by itscopper color, and it generally floats to the surface in theformaldehyde-water solutions used for the production of butynediol.Excess bismuth salts can also digest out of the catalyst and formresidues of other colors.

Life test results showed that catalysts produced from bismuth-freemalachite precursors produced substantial amounts of cuprene during the100-hour life test. Even more cuprene was produced when the catalyst waskept hot in the absence of acetylene, simulating the sudden loss ofacetylene in a butynediol manufacturing operation. Furthermore, when 5%bismuth in the form of bismuth subcarbonate was mixed with bismuth-freemalachite and the mixture was subsequently converted to catalyst,substantial cuprene formation was still evident when the catalyst wasevaluated. A trace of cuprene was also noticed with the catalystcontaining 1% bismuth, but the catalysts made from malachitecoprecipitated with higher amounts of bismuth remained cuprene free.With 2% or more bismuth coprecipitated in the malachite, the resultingcatalyst could be held in an acetylene-free environment for shortperiods such as up to about 1/2 hour at elevated temperatures such asbetween 70° and 95° C. without degradation that causes excessive cupreneformation, which would end the useful life of the catalyst.

At bismuth loadings of 5% and higher, some bismuth separation from thecatalyst results after extended use. Thus it appears that bismuthconcentrations above 4% are less desirable, and concentrations in the 3to 4% range appear optimum for overall performance. One preferredcatalyst with a 3% bismuth content was used in the production ofbutynediol for 20 days without evidence of degradation or cupreneformation. Furthermore, the relatively large and uniform particle sizesof catalysts obtained according to the present invention result ineasier filtration. In butynediol preparation methods wherein thecatalyst system operates as a slurry and the product is removed througha candle filter technique, the larger particle size is able to permitincreased filtration rates.

EXAMPLE 1 Malachite -- 4% Bi Starting Cold

Crystalline particulate synthetic malachite containing 4% bismuth wasprepared in accordance with the invention as follows.

Into a reaction vessel containing 300 cc. of water are simultaneouslyadded two streams. One stream is a saturated solution of Na₂ CO₃ inwater and the other is a water solution containing 100 g. Cu(NO₃)₂.3H₂O, 2.32 g. Bi(NO₃)₃.5H₂ O, 10 cc. HNO₃ and 90 cc. of H₂ O. The streamsare added at rates such as to keep the pH in the precipitation vesselcontinuously at about 6.5, and heat is gradually applied from thebeginning to commence the precipitation. The following table shows therate of solution addition measured in terms of the copper nitratesolution still to be added, time since commencing addition and thetemperature of the reaction mixture.

                  TABLE I                                                         ______________________________________                                        MALACHITE PRODUCTION                                                                                     Solution                                            Time        Temperature   to be Added                                        Minutes      (° C.) (cc. CuNO.sub.3)                                   ______________________________________                                         0           35            150                                                10 (nucleation)                                                                            70            125                                                35                          22                                                72           75            0                                                  ______________________________________                                    

The reaction product was allowed to digest until it reached a pH of 8.0and then was filtered and dried. The particles had an averagecross-sectional dimension of 15-20μ. The product contained 4% bismuthuniformly dispersed through the crystalline particles.

It is desirable to add only about 1/4 to 1/3 of the reactants untilnucleation and conversion occur, which may happen simultaneously, andthen to add the remaining reactants after nucleation to grow thebismuth-containing-malachite crystals.

EXAMPLE 2 Malachite -- 3% Bi Starting Cold

Crystalline particulate synthetic malachite containing 3% bismuth wasprepared in accordance with Example 1, but using 1.74 g. Bi(NO₃)₃.5H₂ O.The following table shows data analogous to that of Example 1, and alsogives the pH at several times during the reaction.

                  TABLE II                                                        ______________________________________                                        MALACHITE PRODUCTION                                                                              Solution                                                  Time    Temperature to be Added                                               Minutes (° C.)                                                                             (cc. CuNO.sub.3)                                                                          pH                                            ______________________________________                                         0      85          140         6.5                                           15      75          125         6.5 (nucleation)                              27      75          100         6.5 (all material                                                             converted to                                                                  malachite, change                                                             pH to 7.5)                                    35      75           50         7.4                                           41      75           25         7.4                                           50      75          0           6.7                                           ______________________________________                                    

The nucleation was accomplished at a pH of 6.5, and then the pH wasincreased to 7.5 to grow the crystals. The crystallizing was finished ata pH of 6.8 to insolubilize all the malachite. The product was thendigested to a pH of 8.0, washed, filtered and dried. The resultingproduct had particles of 15 to 25 microns cross-sectional dimension withgood dispersion of bismuth at the 3% level.

EXAMPLE 3 Catalyst Preparation

In a typical catalyst preparation 45 g. of malachite containing 3%bismuth and 25 g. Cu is charged to a glass vessel with jacket heatingalong with 600 g. of 37% formaldehyde and 2 g. of CaCO₃ for neutralizingthe formic acid generated. A N₂ -diluted C₂ H₂ stream is passed throughthe vessel using a sintered glass frit for gas distribution. Temperatureis controlled between 70° and 80° C. and pressure at 4 to 5 psig. As themalachite is converted to copper acetylide, CO₂ is eliminated and thesystem is thus provided with a vent to effect CO₂ removal. The system isalso equipped with a small recycle gas pump so that unreacted C₂ H₂ isrecycled, and makeup C₂ H₂ and N₂ are added to maintain the pressure.The C₂ H₂ concentration, as measured by gas chromatography in the offgas, is generally maintained in the 2 to 5% by volume range to achievethe most active catalyst. After all CO₂ is eliminated the reactor iscooled, the contents are removed and the catalyst is washed with waterto eliminate product butynediol and unreacted formaldehyde. The catalystthus obtained is stored under water until it is subjected to evaluationwith respect to stability and long term activity.

EXAMPLE 4 Catalyst Evaluation Life Test

For evaluation, the catalyst derived from a 45 g. malachite charge ischarged to a jacketted vessel with 600 cc. of 15% formaldehyde solution.Acetylene gas is passed through a sintered glass frit to achieve thenecessary distribution and mass transfer. Reactor temperature isincreased to 90° C. and after 8 hours to 95° C. Acetylene is fedcontinously as is a 37% formaldehyde solution to maintain a steady state10% formaldehyde concentration. Product is continuously withdrawnthrough a sintered glass filter so that catalyst remains in the reactor.Sodium bicarbonate solution is added continuously to maintain pH in the6.0 to 6.2 region as measured by an in-reactor pH probe. Total reactorpressure is maintained at 5 psig. Activity is measured as weight unitsof C₂ H₂ consumed/hour/weight unit of copper in the reactor and iscalculated continuously from the rate of formaldehyde consumption. Alife test runs for approximately 100 hours or longer after which thesystem is cooled, the catalyst withdrawn, filtered and washed free fromreactants and product and examined for cuprene content. Cuprene isreadily detected by its characteristic copper color and tends to floaton the surface of the water layer under which the evaluated catalyst isstored.

Table III below summarizes the results of life tests with cuprousacetylide catalysts of the invention. When more than 5% bismuth wasused, various colored materials were deposited on the catalyst. Bismuthsalts separate as a result of bismuth digesting out of the catalyst.Above 1% bismuth, cuprene was not detected except in the cases in whichthe bismuth was not coprecipitated with the malachite at temperatures ofthe invention, tests 11 and 12. Catalysts containing 2, 5 and 15%bismuth were exposed to elevated temperatures in the absence ofacetylene without deleterious subsequent formation of cuprene.

                                      TABLE III                                   __________________________________________________________________________    CATALYSIS WITH BISMUTH                                                                    Time Yield                                                        Test                                                                             % Bi                                                                             Time (hrs.)                                                                         (C.sub.2 H.sub.2 /Cu-hr.)                                                             Cuprene                                                                            Remarks                                              __________________________________________________________________________    1  15 210   0.75    --   Bi salt separated                                    2  15 175   0.63    --   Bi salt separated                                    3  10 207   0.6     --   Bi salt separated                                    4  8   85   0.7     --   Bi salt separated                                    5  5  187   0.7-0.6 none                                                      6  3  205   0.7     none clear                                                7  2   99   0.56    none                                                      8  1  105   0.5     visible                                                   9  1  102   0.65    visible                                                   10 0   90   0.5     visible                                                                            malachite without Bi                                 11 5  100   0.5     extensive                                                                          added (BiO).sub.2 CO.sub.3 to malachite                                       without coprecipitating                              12 4   90   0.75    visible                                                                            precipitated at room                                                          temperature (23° C.), Bi                                               separated                                            __________________________________________________________________________

I claim:
 1. In the production of 1,4-butynediol by reaction of acetyleneand formaldehyde in the presence of a cuprous acetylide catalyst, theimprovement comprising use of a catalyst consisting essentially of aparticulate cuprous acetylide complex having uniformly dispersed thereinbismuth in the amount of 2 to 5 percent by weight based on the amount ofcopper present and produced byprecipitating hydrated copper carbonateparticles by the addition to water of solutions of cupric salts andalkali metal carbonate or bicarbonate to form a reaction mixture, saidsolutions being in such proportions as to maintain the pH about in therange of 5.0 to 8.0, nucleating and converting the hydrated coppercarbonate to basic copper carbonate in the reaction mixture at atemperature of at least about 60° C., and growing agglomerates of thenucleated crystalline particles by precipitating basic copper carbonatecontaining bismuth by the addition to the reaction mixture of solutionsof cupric salts, bismuth salts and alkali metal carbonate or bicarbonatein such proportions as to maintain the pH about in the range of 5.0 to8.0 with the reaction mixture at a temperature of at least about 60° C.until the average cross-sectional dimension of the agglomerates ofcrystallites is at least about 10 microns, and then subjecting theagglomerated basic copper carbonate as a slurry in aqueous medium at 50°to 120° C., to the simultaneous action of formaldehyde and acetylene ata partial pressure of not more than 2 atmospheres, said aqueous mediumhaving a pH of 3 to 10 at the initiation of said subjecting, andcontinuing the reaction until said complex is obtained.